As an added bonus for observers in Western Europe and northwestern Africa, Venus will actually be eclipsed by the moon on Monday at 4:15 p.m. UTC and will reemerge later during twilight.

The next time a so-called planetary occultation with Venus will be visible from North America is on the morning of April 22, 2009.

Rare Events

Planetary conjunctions are relatively rare events, especially ones involving such a close encounter between Venus and Jupiter.

"They reach conjunction on average about once a year, although the time interval can range from 34 days to 412 days, and all but 23 percent of these are too close to the sun to observe," said Anthony Cook, astronomical observer at the Griffith Observatory in Los Angeles.

The next conjunction between Jupiter and Venus is on February 16, 2010, when the pair is just over half a degree apart, or the size of one full moon.

Unfortunately that event will be too close to the blinding glare of the sun for us to see.

The next visible conjunction will be on the evening of March 14, 2012, but the two planets will appear farther apart in the sky, separated by more than three degrees.

Heavenly Light

Historically, striking planetary groupings have held special meaning to ancient astronomers and astrologers.

A similarly close conjunction between Venus and Jupiter occurred in June of 2 B.C., and some scholars have connected the event with the Christian nativity story.

According to the Bible, three magi in the East were alerted to the birth of Jesus and led toward Bethlehem by a superbright star—a celestial phenomenon that could be explained by two planets tightly grouped in the sky.

Astronomers say this year's planetary convergence is special because it's occurring at a particularly opportune time of day: in the early evening when nearly everyone worldwide might have a chance to witness it.

"The striking appearance of the conjunction will catch the attention of even those unfamiliar with the sky," Cook said.

"We are naturally attracted to close pairings of bright objects, and the presence of the slender crescent moon will only add to the beauty and awe of the event."